Thin film transistor and display device

ABSTRACT

Provided are a thin film transistor that is capable of suppressing desorption of oxygen and others from an oxide semiconductor layer, and reducing the time to be taken for film formation, and a display device provided therewith. A gate insulation film  22 , a channel protection layer  24 , and a passivation film  26  are each in the laminate configuration including a first layer  31  made of aluminum oxide, and a second layer  32  made of an insulation material including silicon (Si). The first and second layers  31  and  32  are disposed one on the other so that the first layer  31  comes on the side of an oxide semiconductor layer  23 . The oxide semiconductor layer  23  is sandwiched on both sides by the first layers  31  made of aluminum oxide, thereby suppressing desorption of oxygen and others, and stabilizing the electrical characteristics of a TFT  20 . Moreover, since the second layer  32  is made of an insulation material including silicon (Si), the time to be taken for film formation can be reduced compared with a single layer made of aluminum oxide.

TECHNICAL FIELD

The present invention relates to a thin film transistor (TFT) includingan oxide semiconductor layer as a channel, and a display device providedtherewith.

2. Background Art

An oxide semiconductor such as zinc oxide or indium gallium zinc oxide(IGZO) has the excellent characteristics to serve as an active layer ofa semiconductor device, and recently is under development with the aimof application to a TFT, a light-emitting device, a transparentconductive film, and others.

For example, a TFT using an oxide semiconductor is with a high electronmobility and with excellent electrical characteristics compared with theone in which a channel is amorphous silicon (a-Si: H) previously used ina liquid crystal display device. Such a TFT also has advantages ofpossibly achieving a high mobility even at a low temperature of aboutroom temperature.

On the other hand, the oxide semiconductor is known to be not heatresistant enough, and to cause lattice defects due to the desorption ofoxygen, zinc, and others during a heat treatment in a TFT manufacturingprocess. Such lattice defects reduce the resistance of the oxidesemiconductor layer because, electrically, the impurity level becomeslow therewith. Therefore, the resulting operation is performed in thenormally-ON mode, i.e., in the depletion mode, in which a flow of draincurrent is provided even with no application of a gate voltage. As aresult, with the increase of the defect level, the threshold voltage isreduced, thereby increasing a leakage current.

Previously proposed is to lower the defect level on an interface byconfiguring, using amorphous aluminum oxide (Al₂O₃), a gate insulationlayer that comes in contact with a channel layer being an oxidesemiconductor, for example (as an example, refer to Patent Literature1.)

CITATION LIST Patent Literature

-   Patent Literature 1: Specification of U.S. Pat. No. 3,913,756

Non-Patent Literature

-   Non-Patent Literature 1: Cetin Kilic, and 1 other, n-type doping of    oxides by hydrogen, “Applied Physics Letters”, 2002, Volume #81,    issue No. 1, p. 73 to p. 75.

SUMMARY OF INVENTION

With the configuration described in Patent Literature 1, however, thegate insulation layer has the thickness of 100 nm or more, and morepreferably, 200 nm or more because the aluminum oxide is with a slowfilm formation rate, for forming such a thick layer of aluminum oxide,the time to be taken for film formation has been long.

Moreover, other than the lattice defects caused due to the desorption ofoxygen, hydrogen is reported as an element that lowers the impuritylevel in the oxide semiconductor (as an example, refer to Non-PatentLiterature 1.). In other words, if the oxide semiconductor is exposed tothe air, the hydrogen in the air reduces the oxygen in the oxidesemiconductor. As measures taken thereagainst, previously, the TFT isformed thereon with a passivation film (protection film) made of siliconoxide, silicon nitride, or others not to pass therethrough the hydrogenthat much. However, such a previous passivation film is not yetconsidered enough in view of protection, and there thus has been ademand for the development of a passivation film having the enhancedcapabilities of being able to serve as a barrier against the oxygen andhydrogen.

The invention is proposed in consideration of such problems, and a firstobject thereof is to provide a thin film transistor that is capable ofsuppressing desorption of oxygen and others from an oxide semiconductorlayer, and reducing the time to be taken for film formation, and toprovide a display device provided therewith.

A second object of the invention is to provide a thin film transistorthat is capable of suppressing reduction of oxygen in an oxidesemiconductor that is caused by hydrogen in the air, and suppressingdesorption of oxygen and others from an oxide semiconductor layer, andto provide a display device provided therewith.

A first thin film transistor in an embodiment of the invention isprovided with a gate insulation film between a gate electrode and anoxide semiconductor layer. On the side of the gate electrode of theoxide semiconductor layer, and on the side opposite to the gateelectrode, a laminated film is provided. The laminated film includes afirst layer made of aluminum oxide, and a second later made of aninsulation material including silicon (Si).

A second thin film transistor in an embodiment of the invention isprovided, in order on a substrate, a gate electrode, a gate insulationfilm, an oxide semiconductor layer, a channel protection film, asource/drain electrode, and a passivation film. The passivation film ismade of an oxide, nitride, or oxynitride containing one or more ofaluminum (Al), titanium (Ti), and tantalum (Ta).

A first display device in an embodiment of the invention is providedwith a thin film transistor and a display element. The thin filmtransistor therein is configured by the first thin film transistor ofthe invention described above.

A second display device in an embodiment of the invention is providedwith a thin film transistor and a display element. The thin filmtransistor therein is configured by the second thin film transistor ofthe invention described above.

In the first thin film transistor in the embodiment of the invention, alaminated film is provided on the side of the gate electrode of theoxide semiconductor layer, and on the side opposite to the gateelectrode. The laminated film includes the first layer made of aluminumoxide, and the second later made of an insulation material includingsilicon (Si). Accordingly, in the resulting configuration, the oxidesemiconductor layer is sandwiched on both sides by the first layer madeof aluminum oxide. This thus suppresses the desorption of oxygen andothers from the oxide semiconductor layer, thereby stabilizing theelectrical characteristics. Moreover, since the second layer is made ofan insulation material including silicon (Si), the time to be taken forfilm formation can be reduced compared with a previous gate insulationlayer configured by a single layer of aluminum oxide.

In the second thin film transistor in the embodiment of the invention,the passivation film is made of an oxide, nitride, or oxynitridecontaining one or more of aluminum (Al), titanium (Ti), and tantalum(Ta). Such a configuration suppresses hydrogen from reaching the oxidesemiconductor layer so that the reduction of oxygen due to the hydrogenin the air does not occur in the oxide semiconductor layer. Moreover,the desorption of oxygen and others does not occur either in the oxidesemiconductor layer so that the threshold voltage is stabilized in theresulting thin film transistor, and an off current is suppressed fromincreasing.

According to the first thin film transistor in the embodiment of theinvention, on the side of the gate electrode of the oxide semiconductorlayer, and on the side opposite to the gate electrode, provided is thelaminated film including the first layer made of aluminum oxide, and thesecond later made of an insulation material including silicon (Si).Accordingly, in the resulting configuration, the oxide semiconductorlayer can be sandwiched on both sides by the first layer made ofaluminum oxide. This thus suppresses the desorption of oxygen and othersfrom the oxide semiconductor layer, thereby stabilizing the electricalcharacteristics. Moreover, since the second layer is made of aninsulation material including silicon (Si), the time to be taken forfilm formation can be reduced compared with a previous gate insulationlayer configured by a single layer of aluminum oxide.

In the second thin film transistor in the embodiment of the invention,the passivation film is made of an oxide, nitride, or oxynitridecontaining one or more of aluminum (Al), titanium (Ti), and tantalum(Ta). Such a configuration can suppress the reduction of oxygen in theoxide semiconductor layer that is caused by the hydrogen in the air, andalso can suppress the desorption of oxygen and others in the oxidesemiconductor layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A view of a display device in an embodiment of the invention,showing the configuration thereof.

FIG. 2 An equivalent circuit diagram showing an exemplary pixel drivecircuit of FIG. 1.

FIG. 3 A cross sectional view of a TFT of FIG. 2, showing theconfiguration thereof.

FIG. 4 A cross sectional view of a display region of FIG. 1, showing theconfiguration thereof.

FIG. 5 Cross sectional views of the display device of FIG. 1, showing amanufacturing method thereof in order of processes.

FIG. 6 Cross sectional views thereof showing processes subsequent tothose of FIG. 5.

FIG. 7 A cross sectional view of a TFT in a modified example 1, showingthe configuration thereof.

FIG. 8 A cross sectional view of a TFT in a modified example 2, showingthe configuration thereof.

FIG. 9 A cross sectional view of a TFT in a modified example 3, showingthe configuration thereof.

FIG. 10 A cross sectional view of a TFT in a second embodiment of theinvention, showing the configuration thereof.

FIG. 11 Cross sectional views of the TFT of FIG. 10, showing amanufacturing method thereof in order of processes.

FIG. 12 Cross sectional views thereof showing processes subsequent tothose of FIG. 11.

FIG. 13 A diagram showing the study results about a correlation betweenan addition of nitrogen and the density of a passivation film.

FIG. 14 A cross sectional view of a TFT in a third embodiment of theinvention, showing the configuration thereof.

FIG. 15 A diagram showing the characteristics of a TFT when apassivation film therein is a laminated film or a single-layer film.

FIG. 16 A plan view of a module including the display device in theabove embodiment(s), showing the schematic configuration thereof.

FIG. 17 A perspective view of the display device in the aboveembodiment(s), showing the outer view thereof in an application example1.

FIG. 18 (A) is a perspective external view from the front side in anapplication example 2, and (B) is a perspective external view from therear side therein.

FIG. 19 A perspective external view in an application example 3.

FIG. 20 A perspective external view in an application example 4.

FIG. 21 (A) is a front view in the open state in an application example5, (B) is a side view thereof, (C) is a front view in the close state,(D) is a left side view thereof, (E) is a right side view thereof, (F)is a top view thereof, and (G) is a bottom view thereof.

DESCRIPTION OF EMBODIMENTS

In the below, by referring to the accompanying drawings, embodiments ofthe invention are described in detail. Note that the description isgiven in the following order.

1. First Embodiment (an example in which a gate insulation film, achannel protection layer, and a passivation film are each a laminatedfilm in a first thin film transistor)

2. Second Embodiment (an example with a single-layer passivation film ina second thin film transistor)

3. Third Embodiment (an example with a laminated passivation film in thesecond thin film transistor)

4. Modified Example 1 (an example in which a gate insulation film and achannel protection layer are each a laminated film in the first thinfilm transistor)

5. Modified Example 2 (an example in which a gate insulation film and apassivation film are each a laminated film in the first thin filmtransistor)

First Embodiment

FIG. 1 is a diagram showing the configuration of a display device in afirst embodiment of the invention. This display device is for use as anultra-thin organic light-emitting color display device. For example, inthis display device, a TFT substrate 1 that will be described later isprovided thereon with a display region 110, in which pixels PXLC arearranged in a matrix. The pixels PXLC are each configured by any one ofa plurality of organic light-emitting elements 10R, 10G, and 10B eachbeing a display element and will be described later. This display region110 is provided therearound with a horizontal selector (HSEL) 121 beinga signal section, a write scanner (WSCN) 131 and a power supply scanner(DSCN) 132 each being a scanner section.

In the display region 110, signal lines DTL 101 to 10 n are arranged ina column direction, and in a row direction, scan lines WSL 101 to 10 mand power supply lines DSL 101 to 10 m are arranged. At eachintersection between the signal lines DTL and the scan lines WSL,provided is a pixel circuit 140 including the organic light-emittingelement PXLC (any one of 10R, 10G, and 10B (sub pixel)). The signallines DTL are each connected to the horizontal selector 121, and fromthis horizontal selector 121, the signal lines DTL are each providedwith a video signal. The scan lines WSL are each connected to the writescanner 131. The power supply lines DSL are each connected to the powersupply line scanner 132.

FIG. 2 is a diagram showing an example of the pixel circuit 140. Thepixel circuit 140 is an active-type drive circuit including a samplingtransistor 3A, a drive transistor 3B, a storage capacity 3C, and alight-emitting element 3D being the organic light-emitting element PXLC.In the sampling transistor 3A, a gate thereof is connected to thecorresponding scan line WSL 101, either a source or a drain thereof isconnected to the corresponding signal line DTL 101, and the remaining isconnected to a gate g of the drive transistor 3B. In the drivetransistor 3B, a drain d thereof is connected to the corresponding powersupply line DSL 101, and a source s thereof is connected to an anode ofthe light-emitting element 3D. In the light-emitting element 3D, acathode thereof is connected to a ground wiring pattern 3H. Note herethat this ground wiring pattern 3H is provided for a shared use amongall of the pixels PXLC. The storage capacity 3C is connected between thesource s and the gate g in the drive transistor 3B.

The sampling transistor 3A is conducted in accordance with a controlsignal coming from the corresponding scan line WSL 101, and is operatedto sample the signal potential of a video signal provided by thecorresponding signal line DTL 101 for storage into the storage capacity3C. The drive transistor 3B is operated to, after receiving a currentsupply from the power supply line DSL 101 at a first potential, providea drive current to the light-emitting element 3D in accordance with thesignal potential stored in the storage capacity 3C. The light-emittingelement 3D is so configured as, by the drive current provided as such,to emit light with the luminance in accordance with the signal potentialof the video signal.

FIG. 3 is a diagram showing the cross-sectional configuration of a TFT20 configuring the sampling transistor 3A and the drive transistor 3Bshown in FIG. 2. The TFT 20 is an oxide semiconductor transistorincluding, on a substrate 10 in order, a gate electrode 21, a gateinsulation film 22, an oxide semiconductor layer 23, a channelprotection layer 24, a source/drain electrode 25, and a passivation film26, for example. Herein, the oxide semiconductor means an oxide of zinc,indium, gallium, tin, or a mixture thereof, and is known to have theexcellent semiconductor characteristics.

The gate electrode 21 is for controlling, by a gate voltage forapplication to the TFT 20, the electron density in the oxidesemiconductor layer 23. The gate electrode 21 has the two-layerconfiguration of a molybdenum (Mo) layer with the thickness of 50 nm,and an aluminum (Al) or aluminum alloy layer with the thickness of 400nm, for example. The aluminum alloy layer is exemplified by analuminum-neodymium alloy layer.

The gate insulation film 22, the channel protection layer 24, and thepassivation film 26 are each in the laminate configuration of a firstlayer 31 and a second layer 32. The first layer 31 is made of aluminumoxide, and the second layer 32 is made of an insulation materialincluding silicon (Si). With such a configuration, in the resultingdisplay device, the desorption of oxygen and others can be suppressedfrom occurring in the oxide semiconductor layer 23, and the time to betaken for formation of the gate insulation film 22, the channelprotection layer 24, and the passivation film 26 can be reduced.

The first layer 31 is for stabilizing the electrical characteristics ofthe TFT 20 by suppressing desorption of oxygen and others from occurringin the oxide semiconductor layer 23, and by suppressing any change ofthe carrier concentration in the oxide semiconductor layer thanks to theexcellent gas barrier resistance of the aluminum oxide.

The second layer 32 is for reducing the time to be taken for filmformation of the gate insulation film 22, the channel protection layer24, and the passivation film 26 without causing degradation of thecharacteristics of the TFT 20. The second layer 32 preferably includesone or more of a silicon oxide film, a silicon nitride film, and asilicon oxynitride film.

The oxide semiconductor shows a large change of the carrierconcentration in the semiconductor due to the influence of oxygen andmoisture content. As a result, when the TFT 20 is driven for a longtime, or during the manufacturing process of the TFT 20, the TFT 20often shows a change of electrical characteristics. In considerationthereof, by sandwiching the oxide semiconductor layer 23 between thefirst later 31 of the gate insulation film 22 and the first layer 31 ofthe channel protection layer 24, the influence of gas such as oxygen canbe reduced, thereby being able to increase the stability and reliabilityof the electrical characteristics of the TFT 20.

The first and second layers 31 and 32 are preferably disposed one on theother so that the first layer 31 comes on the side of the oxidesemiconductor layer 23. This is because such a configuration allows tosandwich the oxide semiconductor layer 23 directly between the firstlayer 31 of the gate insulation film 22 and the first layer 31 of thechannel protection layer 24 so that the resulting effects can beenhanced thereby.

Moreover, the TFT 20 can be increased in stability and reliability to afurther degree by covering the oxide semiconductor layer 23 by the firstlayer 31 of the passivation film 26 so that the resulting effects can beenhanced thereby.

The first layer 31 of the gate insulation film 22 preferably has thethickness of 10 nm or more but 100 nm or less, and the second layer 32thereof preferably has the thickness of 100 nm or more but 600 nm orless, for example. The first layer 31 of the channel protection layer 24preferably has the thickness of 10 nm or more but 100 nm or less, andthe second layer 32 thereof preferably has the thickness of 100 nm ormore but 600 nm or less, for example. The first layer 31 of thepassivation film 26 preferably has the thickness of 10 nm or more but100 nm or less, and the second layer 32 thereof preferably has thethickness of 100 nm or more but 600 nm or less, for example.

The oxide semiconductor layer 23 has the thickness of 20 nm or more but100 nm or less, and is made of indium gallium zinc oxide (IGZO), forexample.

The source/drain electrode 25 is made of a metal material such asmolybdenum, aluminum, or titanium, or is configured by a multi-layerfilm made of such metal materials. A specific configuration of thesource/drain electrode 25 preferably is a laminated film including, fromthe side of the oxide semiconductor layer 23, a molybdenum layer 25Awith the thickness of 50 nm, an aluminum layer 25B with the thickness of500 nm, and a titanium layer 25C with the thickness of 50 nm, forexample. The reasons thereof are as below. In each of the organiclight-emitting elements 10R, 10G, and 10B that will be described later,if an anode 52 is made of a metal material mainly including aluminum, aneed arises to apply wet etching to these anodes 52 using a mixedsolution of phosphoric acid, nitric acid, acetic acid, and others. Inthis case, as is very low in etching rate, the titanium layer 25C can beremained on the side of the substrate 10. As a result, this accordinglyenables to connect the titanium layer 25C on the side of the substrate10 to cathodes 55 of the organic light-emitting elements 10R, 10G, and10B that will be described later.

Note here that, depending on the use and application of the TFT 20, thesource/drain electrode 25 may be configured also by a laminated film ofa molybdenum layer, an aluminum layer, and another molybdenum layer, ora laminated film of a titanium layer, an aluminum layer, and anothertitanium layer.

FIG. 4 is a diagram showing the cross-sectional configuration of thedisplay region 110. In the display region 110, the organiclight-emitting elements 10R, 10G, and 10B are arranged in orderaltogether like a matrix. The organic light-emitting elements 10R eachemit light of red, the organic light-emitting elements 10G each emitlight of green, and the organic light-emitting elements 10B each emitlight of blue. The organic light-emitting elements 10R, 10G, and 10B areeach shaped like a strip in the planer view, and any of the adjacentorganic light-emitting elements 10R, 10G, and 10B form a pixel.

The organic light-emitting elements 10R, 10G, and 10B each have thelaminate configuration including, in order on the TFT substrate 1 via aflat insulation film 51, the anode 52, an electrode-to-electrodeinsulation film 54, an organic layer 53 including a light-emitting layerthat will be described later, and the cathode 55.

Such organic light-emitting elements 10R, 10G, and 10B are each coveredas required by a protection layer 56 made of silicon nitride (SiN),silicon oxide (SiO), or others. Moreover, such a protection layer 56 isaffixed entirely thereover with a sealing substrate 71 via an attachmentlayer 60 so that it is sealed. The sealing substrate 71 is made of glassor others, and the attachment layer 60 is made of thermosetting resin,ultraviolet curable resin, or others. The sealing substrate 71 may beprovided with, as required, a color filter 72, and a light shieldingfilm (not shown) as a black matrix.

The flat insulation film 51 is for making flat the surface of the TFTsubstrate 1, which is formed with the pixel drive circuit 140 includingthe sampling transistor 3A and the drive transistor 3B constituted bythe TFT 20 described above. Such a flat insulation film 51 is preferablymade of a material with a good pattern accuracy because a minuteconnection hole 51A is formed thereon. Such a material for the flatinsulation film 51 includes an organic material such as polyimide, or aninorganic material such as silicon oxide (SiO₂), for example. The drivetransistor 3B shown in FIG. 2 is electrically connected to the anode 52via the connection hole 51A formed to the flat insulation film 51.

The anode 52 is formed so as to correspond to each of the organiclight-emitting elements 10R, 10G, and 10B. The anode 52 has a functionas a reflection electrode that reflects light generated on thelight-emitting layer, and configuring it to have a reflectioncoefficient as high as possible is desirable in view of increasing thelight-emission efficiency. The anode 52 has the thickness of 100 nm ormore but 1000 nm or less, for example, and is made of a metal elementsuch as silver (Ag), aluminum (Al), chromium (Cr), titanium (Ti), iron(Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), copper (Cu), tantalum(Ta), tungsten (W), platinum (Pt), gold (Au), or others, or alloysthereof.

The electrode-to-electrode insulation film 54 is for insulating theanode 52 and the cathode 55 from each other without fail, and forforming the light-emitting region in any desired shape with a goodaccuracy. The electrode-to-electrode insulation film 54 is made of anorganic material such as polyimide, or an inorganic insulation materialsuch as silicon oxide (SiO₂), for example. The electrode-to-electrodeinsulation film 54 has an aperture portion corresponding to thelight-emitting region of the anode 52. Note that the organic layer 53and the cathode 55 may be provided not only in the light-emitting regionbut also on the electrode-to-electrode insulation film 54 next to eachother. However, light emission occurs only in the aperture portion ofthe electrode-to-electrode insulation film 54.

The organic layer 53 has the laminate configuration including, in orderfrom the side of the anode 52, a hole injection layer, a hole transportlayer, a light-emitting layer, and an electron transport layer (all notshown), for example. The layers other than the light-emitting layer maybe provided as required. The organic layer 53 is not necessarily in onespecific configuration, and may vary in configuration depending on thecolor of light emission by the organic light-emitting elements 10R, 10G,and 10B. The hole injection layer is a buffer layer being not only forincreasing the efficiency of hole injection but also for preventingleakage. The hole transport layer is for increasing the efficiency ofhole transport to the light-emitting layer. The light-emitting layer isfor generation of light as a result of recombination between electronsand holes with the application of an electric field. The electrontransport layer is for increasing the efficiency of electron transportto the light-emitting layer. Note that the organic layer 53 is notrestricted in material as long as it is a general low-molecular ormacromolecular organic material.

The cathode 55 has the thickness of 5 nm or more but 50 nm or less, andis made of a metal element such as aluminum (Al), magnesium (Mg),calcium (Ca), sodium (Na), or others, or alloys thereof, for example.Among all, the preferable material is alloys of magnesium and silver(MgAg alloys), or alloys of aluminum (Al) and lithium (Li) (AlLialloys). The cathode 55 may be made of ITO (Indium Tin Complex Oxide) orIZO (Indium Zinc Complex Oxide).

This display device can be manufactured as below, for example.

(Forming Process of TFT Substrate 1)

First of all, the two-layer configuration of a molybdenum (Mo) layerwith the thickness of 50 nm, and an aluminum (Al) layer or aluminumalloy layer with the thickness of 400 nm is formed by, for example,sputtering on the substrate 10 made of glass. Thereafter, to thistwo-layer configuration, photolithography and etching are applied sothat the gate electrode 21 is formed as shown in FIG. 5(A).

Thereafter, also as shown in FIG. 5(A), the second layer 32 of the gateinsulation film 22 made of the abode-described material with theabove-described thickness is formed by, for example, plasma CVD(Chemical Vapor Deposition) on the entire surface of the substrate 10.

Next, as shown in FIG. 5(B), the first layer 31 of the gate insulationfilm 22 made of the abode-described material with the above-describedthickness is formed by atomic layer deposition or sputtering, forexample.

After the formation of the first layer 31 of the gate insulation film22, also as shown in FIG. 5(B), the oxide semiconductor layer 23 made ofthe abode-described material with the above-described thickness isformed by sputtering using an oxide target such as zinc oxide, forexample. At this time, when the oxide semiconductor layer 23 is made ofIGZO, for example, by DC sputtering with a target of IGZO ceramics, theoxide semiconductor layer 23 is formed on the substrate 10 by plasmadischarge with a gas mixture of argon (Ar) and oxygen (O₂). Note herethat, before the plasma discharge, the vacuum vessel is subjected to airexhaust until the degree of vacuum therein reaches 1×10⁻⁴ Pa or lower,and then a gas mixture of argon and oxygen is directed thereinto.Moreover, when the oxide semiconductor layer 23 is made of zinc oxide,for example, the oxide semiconductor layer 23 is formed by RF sputteringwith a target of zinc oxide ceramics, or by DC sputtering in the gasatmosphere including argon and oxygen using a metal target of zinc.

After the formation of the oxide semiconductor layer 23, also as shownin FIG. 5(B), the first layer 31 of the channel protection layer 24 madeof the above-described material with the above-described thickness isformed by atomic layer deposition or by sputtering, for example.

At this time, the first layer 31 of the gate insulation film 22, theoxide semiconductor layer 23, and the first layer 31 of the channelprotection layer 24 is preferably formed continuously by sputtering. Ifthis is the case, the oxide semiconductor layer 23 can be formed in thevacuum with no exposure to the air so that, on the contact interfacebetween the oxide semiconductor layer 23 and the first layer 31 of thegate insulation film 22, and on the contact interface between the oxidesemiconductor layer 23 and the first layer 31 of the channel protectionlayer 24, the resulting interfaces can be favorable with fewer defectsand a low fixed electric charge. This thus leads to the favorabletransistor characteristics and reliability.

After the formation of the first layer 31 of the channel protectionlayer 24, as shown in FIG. 5(C), the second layer 32 of the channelprotection 24 made of the above-described material with theabove-described thickness is formed by CVD, for example. The first andsecond layers 31 and 32 of the channel protection layer 24 are then eachformed in a predetermined shape by photolithography and etching.

Thereafter, as shown in FIG. 6(A), the oxide semiconductor layer 23 isformed in a predetermined shape by photolithography and etching.

Thereafter, by sputtering, for example, the titanium layer 25A is formedwith the thickness of 50 nm, the aluminum layer 25B is formed with thethickness of 500 nm, and the molybdenum layer 25C is formed with thethickness of 50 nm. These layers are then each formed in a predeterminedshape by photolithography and etching. At this time, for example, by wetetching using a mixed solution of phosphoric acid, nitric acid, andacetic acid, for example, the molybdenum layer 25C and the aluminumlayer 25B are subjected to etching, and then by dry etching usingchlorine gas, the titanium layer 25A is subjected to etching. In thismanner, as shown in FIG. 6(B), the source/drain electrode 25 is formed.

After the formation of the source/drain electrode 25, as shown in FIG.6(C), the first layer 31 of the passivation film 26 made of theabove-described material with the above-described thickness is formed byatomic layer deposition or sputtering, for example. When a method in useis atomic layer deposition, trimethylaluminum gas for use as rawmaterial gas is introduced into the vacuum chamber, and an aluminum filmbeing an atomic layer is formed on the surface of the substrate 10.Thereafter, oxygen radical is introduced to the surface of the substrate10 so that the aluminum film is oxidized. The oxygen radical is theresult of exciting ozone gas or oxygen gas by plasma. The aluminum filmformed for the first time has the thickness of the atomic layer, andthus is easily oxidized by ozone or oxygen radical. A uniform aluminumoxide film can be formed on the entire surface of the substrate 10.Thereafter, by repeating a process of forming the aluminum film and aprocess of oxidation, the first layer 31 can be formed with the aluminumoxide film with a desired thickness. With this method, without causing ashortage of the oxygen concentration in the aluminum oxide film, theresulting composition can be at a stoichiometric ratio. As such, thecomposition ratio between aluminum and oxygen can be ideally 2:3 so thatthe resulting first layer 31 can have the excellent electricalcharacteristics and the excellent gas barrier resistance. Moreover, byusing the method of atomic layer deposition, the first layer 31 made ofaluminum oxide can be formed dense with control over the generation ofhydrogen that degrades the electrical characteristics of the oxidesemiconductor layer 23.

Thereafter, by CVD, for example, the second layer 32 of the passivationfilm 26 made of the above-described material with the above-describedthickness is formed. As such, formed is the TFT substrate 1 includingthe TFT 20 of FIG. 3.

(Forming Process of Organic Light-Emitting Elements 10R, 10G, and 10B)

First of all, the TFT substrate 1 is coated entirely thereover with aphotoresist, and then is exposed to light and is developed, therebyforming and baking the flat insulation film 51 and the connection hole51A. Thereafter, by direct-current sputtering, for example, the anode 52made of the above-described material is formed, and then is selectivelysubjected to etching using the technology of lithography, for example,thereby being patterned into a predetermined shape. Thereafter, theelectrode-to-electrode insulation film 54 made of the above-describedmaterial with the above-described thickness is formed by CVD, forexample, and then an aperture portion is formed using the technology oflithography, for example. Thereafter, by vapor deposition, for example,the organic layer 53 and the cathode 55 each made of the above-describedmaterial are formed in order, and the organic light-emitting elements10R, 10G, and 10B are then formed. The resulting organic light-emittingelements 10R, 10G, and 10B are then covered by the protection film 56made of the above-described material.

Thereafter, on the protection film 56, the attachment layer 60 isformed. The color filter 72 is then provided, and the sealing substrate71 made of the above-described material is prepared. The TFT substrate 1and the sealing substrate 71 are then affixed together with theattachment layer 60 disposed therebetween. In such a manner, the displaydevice shown in FIG. 4 is completed.

In this display device, the sampling transistor 3A is conducted inaccordance with a control signal each coming from the scan lines WSL,and a video signal each coming from the signal lines DTL are sampled interms of its signal potential for storage in the storage capacity 3C.Also, the drive transistor 3B is provided with a current from any of thepower supply lines DSL at a first potential, and in accordance with thesignal potential stored in the storage capacity 3C, a drive current isprovided to the light-emitting elements 3D (organic light-emittingelements 10R, 10G, and 10B). The light-emitting elements 3D (organiclight-emitting elements 10R, 10G, and 10B) emit light, by the drivecurrent provided as such, with the luminance in accordance with thesignal potential of the video signals. This light is extracted after thepassage through the cathode 55, the color filter 72, and the sealingsubstrate 71.

In this example, the gate insulation film 22, the channel protectionlayer 24, and the passivation film 26 each have the laminateconfiguration including the first layer 31 made of aluminum oxide, andthe second layer 32 made of an insulation material including silicon(Si). In the resulting configuration, the oxide semiconductor layer 23is sandwiched on both sides by the first layer 31 made of aluminumoxide. Thus, the desorption of oxygen and others can be suppressed fromoccurring in the oxide semiconductor layer 23 so that the thresholdvoltage is stabilized in the TFT 20, and the off current is suppressedfrom increasing. Therefore, the leakage current is reduced in the TFT20, whereby the resulting display can be luminous with a high level ofluminance. Moreover, since the second layer 32 is made of an insulationmaterial including silicon (Si), compared with a previous gateinsulation layer being a single layer of aluminum oxide, the time to betaken for film formation can be shorter.

Furthermore, since the characteristics of the TFT 20 can be uniform, theresulting display quality can be uniform with no roughness. In additionthereto, the TFT 20 can be increased in reliability even if it is drivenfor a long time.

As such, in this embodiment, the gate insulation film 22, the channelprotection layer 24, and the passivation film 26 each have the laminateconfiguration including the first layer 31 made of aluminum oxide, andthe second layer 32 made of an insulation material including silicon(Si). In the resulting configuration, the oxide semiconductor layer 23can be sandwiched on both sides by the first layer 31 made of aluminumoxide. Therefore, the desorption of oxygen and others can be suppressedfrom occurring in the oxide semiconductor layer 23 so that theelectrical characteristics of the TFT 20 can be stabilized. Moreover, byconfiguring the second layer 32 using an insulation material includingsilicon (Si), compared with a previous gate insulation layer being asingle layer of aluminum oxide, the time to be taken for film formationcan be shorter.

Especially, the first and second layers 31 and 32 are disposed one onthe other so that the first layer 31 comes on the side of the oxidesemiconductor layer 23. This thus allows to sandwich the oxidesemiconductor layer 23 directly between the first layer 31 of the gateinsulation film 22 and the first layer 31 of the channel protectionlayer 24 so that the resulting effects can be enhanced more thereby.

Also especially, the gate insulation film 22, the channel protectionlayer 24, and the passivation film 26 each have the laminateconfiguration including the first layer 31 made of aluminum oxide, andthe second layer 32 made of an insulation material including silicon(Si). This allows to sandwich the oxide semiconductor layer 23 betweenthe first layer 31 of the gate insulation film 22 and the first layer 31of the channel protection layer 24, and also to cover it by the firstlayer 31 of the passivation film 26. Accordingly, the TFT 20 can beincreased more in stability and reliability to a further degree so thatthe resulting effects can be enhanced more thereby.

Modified Example 1

Note that, in the first embodiment described above, exemplified is thecase in which the gate insulation film 22, the channel protection layer24, and the passivation film 26 each have the laminate configurationincluding the first layer 31 made of aluminum oxide, and the secondlayer 32 made of an insulation material including silicon (Si).Alternatively, as shown in FIG. 7, only the gate insulation film 22 andthe channel protection layer 24 may each have the laminate configurationincluding the first layer 31 made of aluminum oxide, and the secondlayer 32 made of an insulation material including silicon (Si). Thisconfiguration also enables to reduce the influence of gas such as oxygenby sandwiching the oxide semiconductor layer 23 between the first layer31 of the gate insulation film 22 and the first layer 31 of the channelprotection layer 24, thereby being able to increase the stability andreliability of the electrical characteristics of the TFT 20.

In this case, the passivation film 26 has the thickness of about 300 nm,for example, and is configured by one or more of an aluminum oxide film,a silicon oxide film, a silicon nitride film, and a silicon oxynitridefilm.

Modified Example 2

Still alternatively, as shown in FIG. 8, only the gate insulation film22 and the passivation film 26 may each have the laminate configurationincluding the first layer 31 made of aluminum oxide and the second layer32 made of an insulation material including silicon (Si). Thisconfiguration also enables to reduce the influence of gas such as oxygenby sandwiching the oxide semiconductor layer 23 between the first layer31 of the gate insulation film 22 and the first layer 31 of thepassivation film 26, thereby being able to increase the stability andreliability of the electrical characteristics of the TFT 20.

In this case, the channel protection layer 24 has the thickness of about300 nm, for example, and is configured by one or more of an aluminumoxide film, a silicon oxide film, a silicon nitride film, and a siliconoxynitride film.

Modified Example 3

Note that, in the embodiment described above, exemplified is the case inwhich the first and second layers 31 and 32 of the passivation film 26are disposed one on the other so that the first layer 31 comes on theside of the oxide semiconductor layer 23. Alternatively, as shown inFIG. 9, such layer disposition may be performed so that the second layer32 comes on the side of the oxide semiconductor layer 23. Also in thegate insulation film 22 and the channel protection layer 24, the firstlayer 31 and the second layer 32 may be disposed one on the other sothat the second layer 32 comes on the side of the oxide semiconductorlayer 23.

Second Embodiment

FIG. 10 is a diagram showing the cross-sectional configuration of a thinfilm transistor (TFT) 20B in a second embodiment of the invention. Inthis TFT 20B, a passivation film 26B is configured differently but theremaining configuration is similar to that of the TFT 20 in the firstembodiment described above. Therefore, any corresponding configurationcomponent is provided with the same reference numeral for a description.

The substrate 10, the gate electrode 21, and the source/drain element 25are configured similarly to those in the first embodiment.

A gate insulation film 22B is formed by an insulation film being one ormore types of a silicon oxide film, a silicon nitride film, a siliconoxynitride film, a hafnium oxide film, an aluminum oxide film, atantalum oxide film, and a zirconium oxide film, or oxynitride filmsthereof. Moreover, if the gate insulation film 22B is in the laminateconfiguration of insulation films 31B and 32B including two or moretypes of those, the characteristics of the interface with an oxidesemiconductor layer 23B can be enhanced, and any impurity included inthe substrate 10 is prevented from diffusing to the oxide semiconductorlayer 23B.

Similarly to the first embodiment, the oxide semiconductor layer 23B maybe made of indium gallium zinc oxide (IGZO), or may additionally containan element of tin (Sn), titanium, or others. The oxide semiconductorlayer 23B has the thickness in a range of about 20 nm to 100 nm, forexample.

A channel protection layer 24B is formed by an insulation film being oneor more types of a silicon oxide film, a silicon nitride film, a siliconoxynitride film, a hafnium oxide film, an aluminum oxide film, atantalum oxide film, and a zirconium oxide film, or oxynitride filmsthereof.

The passivation film 26B is made of an oxide, nitride, or oxynitridecontaining one or more of aluminum (Al), titanium (Ti), and tantalum(Ta). With such a configuration, in the TFT 20B, reduction of oxygen andothers due to the hydrogen in the air does not occur in the oxidesemiconductor layer, and desorption of oxygen and others can be alsosuppressed in the oxide semiconductor layer.

Among all, the passivation film 26B is preferably made of aluminumoxynitride or aluminum nitride. This is because the resulting effectscan be enhanced thereby.

The passivation film 26B preferably has the density of 3.0 g/cm³ orhigher but 4.0 g/cm³ or lower. This is because the barrier capabilitiescan be enhanced thereby to prevent the reduction of an oxidesemiconductor in the manufacturing process or by hydrogen in the air,and to prevent the desorption of oxygen in the oxide semiconductor dueto a heat treatment. The passivation film with a higher densitygenerally serves better as a protection film because it does not allowthe oxygen and hydrogen to pass therethrough that much. For information,the ideal bulk density of aluminum oxide (Al₂O₃) is 4.0 g/cm³.

The passivation film 26B is a single-layer film, for example. Thethickness of the passivation film 26B is preferably 10 nm or more but1000 nm or less, and specifically about 50 nm, for example.

The TFT 20B can be manufactured as below.

FIGS. 11 and 12 are each a diagram showing the manufacturing method ofthe TFT 20B in order of processes. First of all, as shown in FIG. 11(A),the substrate 10 similar to that in the first embodiment described aboveis prepared. The gate electrode 21 made of the above-described materialis then formed on the substrate 10 by sputtering or CVD as shown in FIG.11(B), for example.

Next, also as shown in FIG. 11(B), the film 32B of the gate insulationfilm 22B made of the above-described material is formed on the entiresurface of the substrate 10 and the gate electrode 21.

Thereafter, as shown in FIG. 11(C), the film 31B of the gate insulationfilm 22B, the oxide semiconductor layer 23B, and the channel protectionlayer 24B each made of the above-described material with theabove-described thickness are formed in order on the film 32B of thegate insulation film 22B. When the oxide semiconductor film 23B is madeof indium gallium zinc oxide (IGZO), by using the method of DCsputtering with a target of indium gallium zinc oxide ceramics, an oxidesemiconductor is formed on the substrate 10 by plasma discharge using agas mixture of argon (Ar) and oxygen (O₂). Herein, before plasmadischarge, the vacuum vessel is subjected to air exhaust until thedegree of vacuum therein reaches 1×10⁻⁴ Pa or lower, and then the gasmixture of argon and oxygen is introduced thereinto. When the oxidesemiconductor layer 23B is made of zinc oxide, for example, a zinc oxidefilm can be formed for use as the oxide semiconductor layer 23 by RFsputtering with a target of zinc oxide ceramics, or by DC sputtering inthe gas atmosphere including argon and oxygen using a metal target ofzinc.

Thereafter, as shown in FIG. 12(A), the channel protection layer 24B issubjected to patterning by photolithography and etching, for example, toform it into a predetermined shape.

After the patterning of the channel protection layer 24B, by sputtering,for example, the titanium layer 25A, the aluminum layer 25B, and thetitanium layer 25C are formed in this order with the thicknesses ofabout 50 nm, 500 nm, and 50 nm, respectively. Thereafter, by dry etchingusing chlorine gas, the titanium layer 25A, the aluminum layer 25B, andthe titanium layer 25C are subjected to patterning so that, as shown inFIG. 12(B), the source/drain electrode 25 is formed. Note here that thesource/drain electrode 25 can be a laminated film of molybdenum andaluminum for application to a thin-film transistor for use to drive aliquid crystal panel, for example.

After the formation of the source/drain electrode 25, as shown in FIG.12(C), the passivation film 26B made of the above-described materialwith the above-described thickness is formed. The passivation film 26Bis preferably formed by sputtering. The reasons thereof are described inthe below.

The stoichiometric aluminum oxide is reported as having the film densityof about 3.5 g/cm³ to 4 g/cm³, and an aluminum oxide film realizes thefavorable reliability if it is formed by ALD (atomic layer deposition),which is considered as an ideal method of thin-film formation. However,this has problems of the slow throughput in mass production because toomuch time for film formation, and the need for use of an organic metalof aluminum, for example.

On the other hand, the method of sputtering allows to reduce the time tobe taken for film formation but at the same time, the resulting formedaluminum oxide film is not reliable enough as the ALD-formed aluminumoxide due to a large number of oxygen defects therein. In considerationthereof, during the film formation of the aluminum oxide film (thepassivation film 26B), making an addition of nitrogen gas is consideredpreferable. As such, the oxygen defects are compensated by nitrogen sothat the passivation film 26B can be formed dense with a higher density.As specific requirements for the addition of nitrogen gas, for example,an addition of 0.1 to 70% of nitrogen or ammonia (NH₃) gas is preferablewith respect to the entire pressure of 0.1 to 5 Pa.

FIG. 13 is a diagram showing the study results about a correlationbetween the addition amount of nitrogen and the density of aluminumoxide/nitride, and shows the results of nine samples and the averagethereof for cases of no addition of nitrogen, a small addition amount ofnitrogen, and a large addition amount of nitrogen. As is known from FIG.13, the addition of nitrogen increases the density of the aluminumoxide/nitride film by about 0.2 g/cm³. Moreover, increasing theconcentration of nitrogen for addition can increase the density to afurther degree.

This TFT 20B can configure a display device similarly to that in thefirst embodiment described above. The manufacturing method of thedisplay device is the same as that in the first embodiment describedabove.

The display device using this TFT 20B is operated similarly to that inthe first embodiment described above. In this example, the passivationfilm 26B in the TFT 20B is made of an oxide, nitride, or oxynitridecontaining one or more of aluminum (Al), titanium (Ti), and tantalum(Ta). Such a configuration suppresses hydrogen from reaching the oxidesemiconductor layer 23B so that the reduction of oxygen due to thehydrogen in the air does not occur in the oxide semiconductor layer 23B.Moreover, the desorption of oxygen and others does not occur either inthe oxide semiconductor layer 23B so that the threshold voltage isstabilized in the resulting TFT 20B, and an off current is suppressedfrom increasing. As such, the leakage current is reduced in the TFT 20B,whereby the resulting display can be luminous with a high level ofluminance. Moreover, since the characteristics of the TFT 20B can beuniform, the resulting display quality can be uniform with no roughness.In addition thereto, the TFT 20B can be increased in reliability ofdriving.

As such, in this embodiment, the passivation film 26B is made of anoxide, nitride, or oxynitride containing one or more of aluminum (Al),titanium (Ti), and tantalum (Ta). Such a configuration can suppress thereduction of oxygen in the oxide semiconductor layer that is caused bythe hydrogen in the air, and also can suppress the desorption of oxygenand others in the oxide semiconductor layer.

Third Embodiment

FIG. 14 is a diagram showing the cross-sectional configuration of a thinfilm transistor (TFT) 20C in a third embodiment of the invention. Inthis TFT 20C, a passivation film 26C is a laminated film but theremaining configuration is similar to that of the TFT 20B in the secondembodiment described above, and can be manufactured similarly thereto.Therefore, any corresponding configuration component is provided withthe same reference numeral for a description.

The passivation film 26C is a laminated film specifically including alower layer 35C, and an upper layer 36C. The lower layer 35C is made ofoxide including aluminum (Al), and the upper layer 36C is made ofoxynitride or nitride including aluminum (Al). The reasons thereof areas below.

When the passivation film 26C is a single-layer film of theabove-described oxide, the process is executed in the oxygen atmosphereduring film formation by sputtering so that the desorption of oxygen issuppressed from occurring in the oxide semiconductor layer 23B, and theprocess can be executed with the stabilized transistor characteristics.On the other hand, when the passivation film 26C is a single-layer filmof the above-described oxynitride or nitride, since an addition ofnitride is made during the film formation by sputtering as described inthe second embodiment, the effects of the oxygen atmosphere describedabove are decreased, and there thus is a possibility of degrading thetransistor characteristics. With the passivation film 26C being alaminated film as described above, the lower layer 35C made of oxideincluding aluminum (Al) can suppress the desorption of oxygen fromoccurring in the oxide semiconductor layer 23B, and the upper layer 36Cmade of oxynitride or nitride including aluminum (Al) can suppress thepassage of hydrogen.

FIG. 15 is a diagram showing the study results about the shift amount ofa threshold voltage after BTS (Bias Temperature Stress) in cases whenthe passivation film is a single-layer film of aluminum oxide, and whenit is a laminated film of the lower layer 35B made of aluminum oxide,and the upper layer 36C of the aluminum oxynitride. As is known fromFIG. 15, when the passivation film 26B is a laminated film, comparedwith the case when it is a single-layer film, the shift amount of athreshold voltage is smaller. In other words, with the passivation film26B being a laminated film as described above, the threshold voltage ofthe resulting TFT 20C can be stabilized to a further degree so that theoff current can be suppressed from increasing. Moreover, the thin filmtransistor can be increased in reliability of driving.

This TFT 20C can configure a display device similarly to the first andsecond embodiments described above. As to the display device, themanufacturing method, the advantages, and the effects thereof are thesame as those in the first and second embodiments described above.

As such, in this embodiment, the passivation film 26C is a laminatedfilm, specifically, is configured to include the lower layer 35C made ofoxide including aluminum (Al), and the upper layer 36C made ofoxynitride including aluminum (Al). With such a configuration, with thelower layer 35C made of oxide including aluminum (Al), the desorption ofoxygen can be suppressed from occurring in the oxide semiconductor layer23B, and with the upper layer 36C made of oxynitride including aluminum(Al), the passage of the hydrogen can be suppressed.

In the third embodiment described above, exemplified is the case thatthe passivation film 26C is a laminated film including the lower layer35C made of aluminum oxide, and the upper layer 36C made of aluminumoxynitride. Alternatively, the laminated film may include an oxide filmincluding metal and an oxynitride film made of metal other thanaluminum, or may be a multi-layer of two or more layers.

Module and Application Example

In the below, described are application examples of the display devicesdescribed in the above embodiments. The display devices in the aboveembodiments can be applied for use as a display device of any electronicdevice in every field as long as it displays externally-provided videosignals or internally-generated video signals as images or video, e.g.,television devices, digital cameras, notebook personal computers, mobileterminal devices such as mobile phones, or video cameras.

(Module)

The display devices in the above embodiments are each incorporated, as amodule shown in FIG. 16, for example, into various types of electronicdevices such as application examples 1 to 5 that will be describedlater. In this module, for example, on one side of the substrate 10, aregion 210 exposed from the sealing substrate 71 and the attachmentlayer 60 is provided, and this exposed region 210 is formed with anexternal connection terminal (not shown) by extending the wiring of asignal line drive circuit 120, and that of a scan line drive circuit130. The external connection terminal may be provided with a flexibleprinted circuit (FPC) 220 for signal input/output.

Application Example 1

FIG. 17 is a diagram showing the outer appearance of a television deviceto which the display devices of the above embodiments are applied. Thistelevision device is provided with a video display screen section 300including a front panel 310 and a filter glass 320, for example. Thisvideo display screen section 300 is configured by any of the displaydevices of the embodiments described above.

Application Example 2

FIG. 18 is a diagram showing the outer appearance of a digital camera towhich the display devices of the above embodiments are applied. Thisdigital camera is provided with a light-emitting section 410 for flashuse, a display section 420, a menu switch 430, and a shutter button 440,for example. The display section 420 is configured by any of the displaydevices of the embodiments described above.

Application Example 3

FIG. 19 is a diagram showing the outer appearance of a notebook personalcomputer to which the display devices of the above embodiments areapplied. This notebook personal computer is provided with a main body510, a keyboard 520 for an input operation of text or others, and adisplay section 530 for display of images, for example. The displaysection 530 is configured by any of the display devices of theembodiments described above.

Application Example 4

FIG. 20 is a diagram showing the outer appearance of a video camera towhich the display devices of the above embodiments are applied. Thisvideo camera is provided with a main body section 610, a lens 620provided on the front side surface of this main body section 610 forobject shooting, a start/stop switch 630 for use during shooting, and adisplay section 640. The display section 640 is configured by any of thedisplay devices of the embodiments described above.

Application Example 5

FIG. 21 is a diagram showing the outer appearance of a mobile phone unitto which the display devices of the above embodiments are applied. Thismobile phone unit includes an upper chassis 710 and a lower chassis 720that are coupled by a coupling section (hinge section) 730, and isprovided with a display 740, a sub display 750, a picture light 760, anda camera 770, for example. The display 740 or the sub display 750 isconfigured by any of the display devices of the embodiments describedabove.

As such, while the invention has been described in detail by referringto the embodiments, the invention is not restrictive to the embodimentsdescribed above, and numerous other modifications and variations can bedevised. As an example, in the first embodiment described above,exemplified is the case in which the gate insulation film 22, thechannel protection layer 24, and the passivation film 26 are entirely orpartially in the laminate configuration including the first layer 31made of aluminum oxide, and the second layer 32 made of an insulationmaterial including silicon (Si). Alternatively, separately from the gateinsulation film 22, the channel protection layer 24, and the passivationfilm 26, on the side of the gate electrode 21 of the oxide semiconductorlayer 23, and on the side opposite to the gate electrode 21, a laminatedfilm including the first layer 31 made of aluminum oxide, and the secondlayer 32 made of an insulation material including silicon (Si) may beprovided.

Moreover, for example, as to the layers described in the aboveembodiments and others, the material, the thickness, or the method offilm formation, and the requirements for film formation are not allrestrictive, and any other materials and thicknesses will also do, orany other methods for film formation and requirements for film formationwill also do.

Further, in the above embodiments and others, the configuration of theorganic light-emitting elements 10R, 10B, and 10G is specificallydescribed, but there is no need to include every layer, or any otherlayers may be additionally provided.

Still further, the invention is applicable to a display device using notonly such organic light-emitting elements but also any other types ofdisplay elements such as liquid crystal display elements, inorganicelectroluminescent elements, display elements of electro-deposition typeor electro-chromic type, or others.

1-15. (canceled)
 16. A thin film transistor comprising: a gateinsulation film between a gate electrode and an oxide semiconductorlayer, wherein on a side of the gate electrode and on a side opposite tothe gate electrode of the oxide semiconductor layer, a laminated filmincluding a first layer made of aluminum oxide and a second layer madeof an insulation material including silicon (Si) is provided.
 17. Thethin film transistor according to claim 16, wherein: the first layer andthe second layer are disposed one on the other with the first layerpositioned on a side of the oxide semiconductor layer.
 18. The thin filmtransistor according to claim 16, wherein: a substrate is providedthereon, in order, with the gate electrode, the gate insulation film,the oxide semiconductor layer, a channel protection film, source/drainelectrodes, and a passivation film, and the gate insulation film and oneor both of the channel protection film and the passivation film are eachthe laminated film.
 19. The thin film transistor according to claim 17,wherein: a substrate is provided thereon, in order, with the gateelectrode, the gate insulation film, the oxide semiconductor layer, achannel protection film, source/drain electrodes, and a passivationfilm, and the gate insulation film and one or both of the channelprotection film and the passivation film are each the laminated film.20. The thin film transistor according to claim 16, wherein: the secondlayer includes one or more of a silicon oxide film, a silicon nitridefilm, and a silicon oxynitride film.
 21. A thin film transistor,wherein: a substrate is provided thereon with, in order, a gateelectrode, a gate insulation film, an oxide semiconductor layer, achannel protection film, source/drain electrodes, and a passivationfilm, and the passivation film is made of an oxide, nitride, oroxynitride containing one or more of aluminum (Al), titanium (Ti), andtantalum (Ta).
 22. The thin film transistor according to claim 21,wherein: the passivation film is made of aluminum oxynitride or aluminumnitride.
 23. The thin film transistor according to claim 21, wherein:the passivation film has a density of 3.0 g/cm³ or higher but 4.0 g/cm³or lower.
 24. The thin film transistor according to claim 21, wherein:the passivation film is a single-layer film.
 25. The thin filmtransistor according to claim 22, wherein: the passivation film is alaminated film.
 26. The thin film transistor according to claim 25,wherein: the laminated film includes a lower layer made of oxideincluding aluminum (Al), and an upper layer made of oxynitride ornitride including aluminum (Al).
 27. The thin film transistor accordingto claim 21, wherein: the passivation film is formed by sputtering. 28.A display device comprising: a thin film transistor; and a displayelement, wherein the thin film transistor includes a gate insulationfilm between a gate electrode and an oxide semiconductor layer, and on aside of the gate electrode and on a side opposite to the gate electrodeof the oxide semiconductor layer, a laminated film including a firstlayer made of aluminum oxide and a second layer made of an insulationmaterial including silicon (Si) is provided.
 29. The display deviceaccording to claim 28, wherein: the display element is an organiclight-emitting element including, in order from a side of the thin filmtransistor, an anode, an organic layer including a light-emitting layer,and a cathode.
 30. A display device, comprising: a thin film transistor;and a display element, wherein the thin film transistor includes inorder on a substrate, a gate electrode, a gate insulation film, an oxidesemiconductor layer, a channel protection film, a source/drainelectrode, and a passivation film, and the passivation film is made ofan oxide, nitride, or oxynitride containing one or more of aluminum(Al), titanium (Ti), and tantalum (Ta).
 31. The display device accordingto claim 30, wherein: the display element is an organic light-emittingelement including, in order from a side of the thin film transistor, ananode, an organic layer including a light-emitting layer, and a cathode.